The Distance Duality Relation from Strong Gravitational Lensing

Abstract: Under very general assumptions of metric theory of spacetime, photons traveling along null geodesics and photon number conservation, two observable concepts of cosmic distance, i.e. the angular diameter and the luminosity distances are related to each other by the so-called distance duality relation (DDR) $D^L=D^A(1+z)^2$. Observational validation of this relation is quite important because any evidence of its violation could be a signal of new physics. In this paper we introduce a new method to test DDR based on strong gravitational lensing systems and type Ia supernovae under a flat universe. The method itself is worth attention, because unlike previously proposed techniques, it does not depend on all other prior assumptions concerning the details of cosmological model. We tested it using a new compilation of strong lensing systems and JLA compilation of type Ia supernovae and found no evidence of DDR violation. For completeness, we also combined it with previous cluster data and showed its power on constraining DDR. It could become a promising new probe in the future in light of forthcoming massive strong lensing surveys and because of expected advances in galaxy cluster modlelling.